The present invention relates in general to network and in particular link failure in the network. More particularly, the present invention relates to re-enabling devices that have been disabled and that are integral parts of the network.
Numerous vendors and potential users (Service Providers) have expressed the need to integrate Ethernet link technologies with their existing infrastructure at a low cost, while providing the manageability and remote diagnostic capabilities traditionally offered by circuit switched technologies.
The Two Port MAC Relay (TPMR) project, undertaken currently by IEEE802.1aj specifies the function of a MAC (Media Access Control) Relay with two MACs and the protocols and procedures to support its operation. A TPMR device is transparent to all frame-based media independent protocols except those explicitly addressed to this device. It is remotely manageable through at least one of its external MACs and is capable of signaling a failure of either of the MAC's connected Local Area Network (LAN) links through the other MAC in the TPMR.
The project is meant to also address issues related to link loss signaling and remote diagnosis, as the current lack of a standardized solution is impeding the growth of the demarcation device industry.
TPMR devices support, among other protocols, a link failure notification mechanism. The detection of a link failure on a port of the TPMR triggers notification of such a failure to the other port of the TPMR. In principle, if a link failure is detected on one port, the link failure propagation entity on the TPMR will periodically transmit TPMR link failure Packet Data Units (PDUs) through the other port. Once the failed link returns to normal operation, periodic transmissions of TPMR link failure frames thorough the other port is stopped. One problem is that the current state machine diagrams as described in P802.1aj/D1.4 (TPMR project) do not include a mechanism that would allow a disabled downstream port to be re-enabled if the disabled downstream port was the result of a propagating link failure PDU that does not enable the capability of responding to link failure PDUs.